Automotive vehicles include evaporative emissions control, or evap, systems to minimize the release of hydrocarbons into the atmosphere. Government regulations require on-board diagnostics for evap systems such as leak detection. When an emissions leak is detected, an automotive repair technician or mechanic may conduct a smoke test to locate the leak so that the leaking component may be repaired or replaced. Such tests require the use of a smoke tester, an apparatus that generates smoke by heating mineral oil.
However, the typical smoke tester is large, expensive, and requires intrusive connections and disconnections to the evaporative emissions system that can introduce variability and new leaks in the system. New leaks in the system could exacerbate the release of hydrocarbons into the atmosphere. Furthermore, the design and use of smoke testers may be inconsistent and provide variable diagnostics depending on the location of the leak, size of the leak, etc.
The inventors herein have recognized the above issues and have devised systems and methods to address them. In particular, systems and methods for smoke testing an evaporative emissions control system of a vehicle using exhaust gas are disclosed. In one example, a method for an engine comprises: during a first condition, routing exhaust gas to a sealed fuel system; and pressurizing the fuel system with the exhaust gas such that exhaust gas will escape from a leak in the fuel system. In this way, the location of an evap system leak may be detected using an on-board smoke test that creates a visual indication for technicians. Further, such operation provides for controlled evaporative emission leak location diagnostics that can lead to decreased emissions while reducing the possibility of degrading vehicle components.
In another example, a method for a vehicle including an evaporative emissions system coupled to an exhaust system comprises: closing a canister purge valve and a canister vent valve responsive to receiving instructions to initiate a smoke test; adjusting a combustion air-fuel ratio to a rich setpoint to generate smoke; opening an exhaust flow valve to allow exhaust gas from the exhaust system to flow into the evaporative emissions system; closing the exhaust flow valve responsive to an evaporative emissions system pressure at a threshold; monitoring a pressure decay rate responsive to closing the exhaust flow valve; and estimating a leak size using the pressure decay rate. In this way, the location and the size of an evap system leak may be determined without the need for, and without using, expensive off-board testing equipment.
In another example, an evaporative emissions system coupled to an internal combustion engine in a vehicle comprises: a canister containing an adsorbent material, the canister fluidly coupled to a fuel system and an engine intake; a canister purge valve positioned downstream of the canister and upstream of the engine intake; a canister vent valve positioned in a vent line upstream of the canister and downstream of an atmosphere; an exhaust flow valve positioned within an exhaust cross passage, the exhaust cross passage coupled between the vent line and an exhaust passage; a controller configured with instructions stored in non-transitory memory that when executed cause the controller to: close the canister purge valve and the canister vent solenoid responsive to a smoke test initiation; open the exhaust flow valve to allow exhaust gas to enter the evaporative emissions system; and close the exhaust flow valve responsive to an evaporative emissions system pressure above a threshold. In this way, a vehicle may include all of the hardware necessary to identify an evap system leak using exhaust gas without the need for expensive test equipment.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.